Wood element hygrostat



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wm w April 11, 1950 Patented Apr. 11, 1950 WOOD ELEMENT HYGROSTATSeymour J. Johnson, Madison, Wis, dedicated to the free use of theUnited States the People in the territory of Application May 22, 1946,Serial No. 671,482

2 Claims.

(Granted under the act oi March 3, amended April 30, 1928; 370 0.

This application is made under the act of March 3, 1883, as amended bythe act of April 30, 1928, and the invention herein described, ifpatented, may be manufactured and used by or for the Government of theUnited States of America for governmental purposes without the paymentto me of any royalty thereon.

I hereby dedicate the invention herein described to the free use of thepeople in the territory of the United States to take effect on thegranting of a patent to me.

My invention relates to improvements in construction of a humiditycontroller called a hygrostat in which the shrinkage and swelling of awood element is used as a means of controlling the relative humidity indrying or conditioning chambers.

Humidity control is accomplished in conventional manner by the automaticopening and closing of valves on steam or water spray lines, or

of dampers in the vent ducts. The valves and dampers are operated bycompressed air, or electrically, or by other means. In the air system,the action of the wood element opens or closes an air leakage port ornozzle and thus operates an air valve which is connected to anair-operated diaphragm valve on a steam or water spray line, or which isconnected to the dampers in the vent ducts. In the electric currentsystem, the action of the wood element operates a microswitch, or makesor breaks contact points and thus operates an electric motor, or motorvalve, that is connected to either steam or water line, or to the ventduct dampers.

Accurate control of conditions has been obtained with my hygrostat, andfor steady conditions, the control is reliable and requires practicallyno attention, except during the first few hours when constant adjustmentis required while the wood is changing to the required equilibriummoisture content.

The common method of control is by wet and dry bulb temperature-controlinstruments. In this system, accuracy of humidity control depends oncontinuous maintenance of both wet and dry bulb temperatures at thedesired setting. Accurate control may be lost if the water supply or aircirculation fails, the wet bulb wick becomes dirty, or the dry bulbtemperature is accidentally raised beyond the compensating power ofnormal heat losses of the drying or conditioning chamber.

Rigid hygroscopic substances, such as wood, which shrink or swell withchanges in moisture content have been used to control relative hu- 1883,as G. 757) midity. The degree to which control is gained by a hygrostatcontaining such a substance as the sensitive element is dependent uponthe relationship between temperature of the air, relaive humidity, andthe equilibrium moisture content of the element. The wood elementhygrostats which have been employed have lacked sensitivity, have notbeen capable of easy adjustment or calibration from either inside oroutside of the conditioned chamber, or have exposedelectrical contactssubject to corrosion inside the conditioned chamber. The wood elementsin these hygrostats have not been capable of easy replacement, have beensubject to breakage during adjustment, shutdown, or failure, or havebeen subject to stresses which cause distortion and subsequentmaladjustment.

The objects of my improvement are to provide. first, a free actingarrangement of the wood element that permits easy calibration,adjustment, and replacement, and also operation without restraintmechanism that operates without lost motion and permits smooth andaccurate adjustments and calibration for desired humidity conditionsover a wide range.

I attain these objects by mechanism illustrated in the accompanyingdrawing, in which Figure 1 is a face view showing the end grain surfaceof the wood section and the spiral pattern 01 the adjusting cam; Figure2 is a side view showing principally the mounting arrangement; Figure 3is a view in section at line 3-3; and Figure 4 is a view of the airnozzle operating means employed when the hygrostat is placedhorizontally.

Thestraight, end-grain wood section I is s11pported freely on the edgeof the spiral-shaped metal cam disc 2 by means of a grooved rod 8 whichis connected to the wood element I through the coupling sleeve 3.Adjustments to obtain desired humidities are obtained from outside ofthe drying or conditioning room by rotating cam 2. The latter is mountedupon adjusting rod 4, which is supported by frame l5 and which extendsthrough the wall 5 of the drying or conditioning chamber. The adjustinrod 4 is provided with a hand wheel l9 which may be cali brated andgraduated in cquilbrium moisture content or otherwise. The device 20 mayserve as a pointer and as a look as well. Top plate It supports nozzle8, and also the pivot mounting M for lever 1. Plate 16 and guide plates2| and 22 are supported on rods 23 and 24. Rods 6 and I3 move in holesin members I5, Ii, 2| and 22. Extensions on members l5 and 2| serve asand breakage; and second, a cam-type brackets for convenient wallmounting. The coupling sleeves 3 are attached by pins l1 and ti eningbolts l8. so that the wood element I can be removed or installed quicklyand easily. As the Wood element I changes in lengthby changes in airconditions, it raises or lowers lever arm I on air nozzle 8 withpractically no restraint, by means of the projecting nut 9 on theconnecting rod l3. This action on air nozzle 8 through air line I2operates a diaphragm valve on a spray line or a diaphragm-operated leverconnected to the vent duct dampers.

The mounting for pivot I l is adjustable, that is, it may be raised orlowered. Mounting of nozzle 8 may likewise be adjustable, as indicatedby dotted lines. Nozzle 8 is adlustably positioned in slot 25.

Lever I I, pivoted at 28, is also raised or lowered by movement of l,and operates an electric microswitch I (or contact points) as a means ofstarting and stopping a control motor on either the spray line or ventsystem. The position of switch I0 is adjustable in slots 26. Lever II ismoved upwardly by conventional spring means in the switch.

The invention contemplates the use of auxiliary fittings such as acounterweight attached to the supporting rod 6 above guide plate 22 or asmall spring 21 inserted between guide plate 22 and a pin installed inrod 6 below guide plate 22 to assist in maintaining contact of rod 6with cam 2 when switch I0 is used. In applications where an electricalcurrent system must be operated at a high humidity, rod l3 may beextended through a hole in the roof of the chamber so that themicroswitch l0 or contact points may be located outside of the chamber.

The invention contemplates the simultaneous use of one or more operatingelements, such as nozzle 8 and switch ID, in one instrument, and in anydesired combination of air and electric operation.

Although in the preferred embodiment of the invention the hygrostat ismounted vertically, it can be mounted horizontally or in any otherrelative position if the auxiliary spring between guide plate 22 and thepin in rod 6 is used. For horizontal mounting with air operation thehygrostat is placed so that lever 7 extends downwardly and is not quitevertical when in a position closing nozzle 8. This is shown in Figure 4.A small counterweight may be attached to lever 1. For horizontalmountings with electrical operation no modification other than theauxiliary spring is needed.

A straight end-grain wood section signifies that the saw cut isapproximately perpendicular to the axis of the tree, and that theprincipal wood cells lie with their axes approximately perpendicular tothe planes of sawing. The wood elements I have used consist oftransverse sections, about g-inch thick, cut from 1- by 10-inch flatsawed boards.

Having thus described my invention, I claim:

1. A hygrostat comprising a frame and a device that expands andcontracts in response to changes in humidity, said device comprising avertical elongated straight end-grain wood section subject to nocompressive force and no compressive restraint longitudinal to thelength of the wood section. support means rigidly attached adjacent thelower end of the wood section and constrained to upward and downwardmovement by guide means mounted upon the frame, means providing avertically adjustable surface upon which the support means rests. secondsupport means comprising a rod fixedly attached adjacent the upper endof the wood and constrained to upward and downward movement by secondguide means mounted upon the frame, a pivoted element an arm of which ismoved downwardly by the second support means upon contraction of thewood section, the rod carrying an abutment in contact withthe upper sideof the arm to move it downwardly as aforesaid and which arm is releasedby the abutment and is free to move upwardly upon upward expansion ofthe wood section, the upward movement of the arm being under applicationof a force other than that of the expanding wood section, the pivotedelement offering no restraint to expansion of the wood section, thepivoted element bein an actuating means for a humidity control device.

2. A hygrostat comprising a frame and a device that expands andcontracts in response to changes in humidity, said device comprisin anelongated straight end-grain wood section subject to no compressiveforce, and no compressive restraint longitudinal to the length of thewood section, support means rigidly attached adjacent to one end of thewood section and constrained by guide means mounted upon the frame tomovement longitudinal to the length of the wood section, means providinga longitudinally adjustable surface against which the support meansabuts, means bearing upon the guide means and the support means to holdthe support means against the said longitudinally adjustable surface, arod rigidly attached to the other end of the wood section, guide meansmounted upon the frame to constrain the movement of the said other endof the wood section to movement in the same longitudinal direction asthe first mentioned lontiudinal movement, a pivoted element an arm ofwhich is. pulled toward said wood section upon contraction of the woodsection, the rod carrying an abutment in contact with the outer face ofthe arm and which arm is released and is free to move in the directionaway from said wood section upon expansion of the wood section, thepivoted element offering no restraint to expansion of the wood section,the said movement away being under application of a force other thanthat of the expanding wood section, the pivoted element being anactuating means for a pneumatic humidity control device.

SEYMOUR J. JOHNSON.

REFERENCES CITED The following references are of record in the 00 fileof this patent:

UNITED STATES PATENTS

